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QLDPhysics2025

QCE Physics 2025

Walkthrough of the 2025 QCE physics exam: what it assessed, strategy tips, and the common errors flagged in the official marker report.

Marks: 60
Time: 120 min
Authority: QCAA
Updated: 2026-05-29

Open the official PDF ->Official marking notes

What this paper assessed

The QCAA Physics external assessment (Paper, 60 marks) is the final 50% summative external, covering Units 3 and 4 of the senior syllabus:

Unit 3 - Gravity and electromagnetism: gravity and motion (projectile and circular motion, gravitational fields and orbits), and electromagnetism (electric and magnetic fields, the motor effect, and electromagnetic induction via Faraday's and Lenz's laws).
Unit 4 - Revolutions in modern physics: special relativity (time dilation, length contraction, mass-energy equivalence), and quantum theory and the Standard Model (the photoelectric effect, atomic spectra, and fundamental particles).

You are given the QCAA formula and data book. The paper mixes objective and short-response items, many of which require extracting data from a graph, applying a relationship, and commenting on the limitations of the model. The extended-response items reward structured reasoning, with each equation stated and its variables defined, units carried, and answers given to appropriate significant figures.

Structure and timing

The paper is 60 marks in 120 minutes (plus perusal) - exactly 2 minutes per mark.

Objective/short items: about 1 minute per mark, banking time for the longer calculations.
Extended calculations and reasoning items: the remaining time at ~2-2.5 min per mark, with multi-step problems getting a moment to sequence the steps.

Use perusal to flag the graph-analysis and multi-step calculation items. List the formula, the substituted values, and the answer with units on separate lines so method marks are visible. Keep the last 8-10 minutes to check units and that every reasoning item names the law applied.

Worked practice questions (exam-style)

Worked example

Question 1 (5 marks): A satellite orbits Earth in a circular orbit of radius $r = 7.0\times10^6\ \text{m}$ . Given $G = 6.67\times10^{-11}\ \text{N m}^2\text{kg}^{-2}$ and Earth's mass $M = 5.97\times10^{24}\ \text{kg}$ , find the orbital speed.

For a circular orbit the gravitational force provides the centripetal force:

\frac{GMm}{r^2} = \frac{mv^2}{r}.

The satellite mass

m

cancels, giving

v = \sqrt{\frac{GM}{r}}.

Substitute:

v = \sqrt{\frac{(6.67\times10^{-11})(5.97\times10^{24})}{7.0\times10^6}} = \sqrt{\frac{3.982\times10^{14}}{7.0\times10^6}}.

v = \sqrt{5.69\times10^{7}} = 7.5\times10^{3}\ \text{m s}^{-1}.

The orbital speed is about

7.5\ \text{km s}^{-1}

. The key step examiners reward is cancelling

m

to show speed is independent of satellite mass.

Worked example

Question 2 (6 marks): A straight conductor of length $0.25\ \text{m}$ carries a current of $3.0\ \text{A}$ at right angles to a uniform magnetic field of $0.40\ \text{T}$ . (a) Calculate the force on the conductor. (b) Explain how this force underlies the operation of a DC motor.

(a) The motor-effect force on a current-carrying conductor is $F = BIL\sin\theta$ , with $\theta = 90^\circ$ so $\sin\theta = 1$ :

F = (0.40)(3.0)(0.25) = 0.30\ \text{N}.

(b) In a DC motor, current flows through a coil in a magnetic field. Each side of the coil carries current in opposite directions, so by $F = BIL$ the two sides experience forces in opposite directions, producing a torque (a couple) that rotates the coil. A commutator reverses the current each half-turn so the torque keeps driving the coil in the same rotational sense, sustaining continuous rotation. The mark for the explanation requires linking $F = BIL$ to the opposing forces producing a turning effect.

Worked example

Question 3 (4 marks): In a photoelectric experiment, light of frequency $f = 8.0\times10^{14}\ \text{Hz}$ ejects electrons from a metal of work function $\phi = 3.0\times10^{-19}\ \text{J}$ . Calculate the maximum kinetic energy of the emitted electrons. ( $h = 6.63\times10^{-34}\ \text{J s}$ .)

Use Einstein's photoelectric equation, $E_{k,\max} = hf - \phi$ :

hf = (6.63\times10^{-34})(8.0\times10^{14}) = 5.30\times10^{-19}\ \text{J}.

E_{k,\max} = 5.30\times10^{-19} - 3.0\times10^{-19} = 2.3\times10^{-19}\ \text{J}.

So the maximum kinetic energy is about

2.3\times10^{-19}\ \text{J}

. Conceptually, this result supports the particle (photon) model of light: each photon delivers a quantised energy

hf

, and only the excess above the work function appears as electron kinetic energy - a fact the wave model cannot explain. Stating that significance earns the reasoning mark.

Common errors students made

The 2025 QCAA marker report flagged missing units, mixing scalar and vector quantities, treating projectile motion as one-dimensional, and forgetting that induced EMF depends on the rate of change of flux rather than the flux itself. Further recurring traps:

Numbers without defined variables or stated equations, which forfeits method marks.
Not cancelling masses or rearranging cleanly in orbital and field problems, leading to wrong powers of ten.
Relativity answers that omit the frame - say which observer measures proper time/length and which measures the dilated/contracted value.
Describing the photoelectric effect or spectra without stating the quantum significance of the result.
Rounding mid-calculation, which shifts the final significant figures.

How to use this paper

Sit the paper in 120 minutes under exam conditions, then mark against the official marking guide and marker report at the QCAA links in the frontmatter, noting where method marks fall. Rebuild every calculation that lost more than half its marks, writing the named equation and defining each variable before substituting. For graph items, practise reading gradient and intercept and stating their physical meaning. Keep an error log sorted by topic (orbits, motor effect, induction, photoelectric, relativity) and re-test that class next session.

Use this paper well

Sit the paper under exam conditions (120 minutes, 60 marks).
Mark yourself against the official QCAA marking notes.
Compare against the Physics hub to find the syllabus dot points this paper tested.

What this paper assessed

Structure and timing

Worked practice questions (exam-style)

Common errors students made

How to use this paper

Use this paper well

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